I am running some experiments on fire ants this spring using instant grits. I've read about grits working, and I reported a bit on them on the blog I started in the member blog area, but I'll report here as well. From my understanding it is the INSTANT variety that is most effective (and probably has the least nutrition for humans, anyway, so they're better left to the ants!)
The results are mixed. When a new bed appears I have sprinkled the contents of a packet around the perimeter of the bed (I found the pre-measured instant grits first, but since then I've found a bulk box of Quaker instant grits at Kroger, and will use about 1/4 cup per bed). I've knocked out new beds with a couple of applications, a couple of days apart, but I have (I think) only managed to annoy and/or move ants on a couple of other older and more established mounds (thus deeper beds, one presumes).
The dogs have licked up the corn off of the concrete when the ant mounds were next to pavement. Better they lick up grits than Amdro or something like that. They're idiots--I think they must get a few ants at the same time.